One of the frequent problems encountered with synthetic polymers is instability on exposure to light, heat and atmospheric conditions, leading to deterioration and color change. Over the years industry has developed many additives that are blended into the polymer to alleviate the problem and is still continuously searching for new materials that will prolong the life of the polymeric product. In addition to the above harmful conditions, many polymers contain metal catalyst residues that can exert adverse effects on the synthetic polymer fiber, film or other article.
The use of additives, collectively called stabilizers, to prevent or inhibit degradation of natural and synthetic materials is known. It is also known that a compound that stabilizes against heat and/or oxygen degradation in a material may not stabilize against light degradation in the same material, and vice versa. It is further known that a compound which exerts some form of stabilization in one type of synthetic or natural material may be completely ineffective in another type of material. Thus, compounds are classified as antioxidants, light stabilizers, heat stabilizers, etc., depending upon the stabilizing effect a particular compound may have on a specific material or type of material. As a consequence, in many cases mixtures of stabilizers are used to obtain desired protection against one or more forms of degradation.
It has now been found that a novel class of polysiloxanes having sterically hindered heterocyclic moieties can be produced that stabilize synthetic polymers against the deleterious effect caused by exposure to light, in particular to ultraviolet light radiation in sunlight.
The use of the heterocyclic piperidine compounds as stabilizers in synthetic polymers has been disclosed. Thus, in U.S. Pat. No. 3,975,357, issued to Murayama et al. on Aug. 17, 1976, a large number of 1-substituted-2,2,6,6-tetramethylpiperidines were disclosed as synthetic polymer stabilizers. However, there is no mention of siloxanes.
In U.S. Pat. No. 4,123,418, issued to Gilg et al. on Oct. 31, 1978, sterically hindered cyclic amines are used to stabilize styrene polymers, such as ABS resins; the patent contains no mention of siloxanes.
The stabilizers disclosed in U.S. Pat. No. 4,177,186, issued to Rody et al. on Dec. 4, 1979, are the 4-siloxy derivatives of alkylated piperidines. Though a large number of siloxys are disclosed none of them are within the scope of this instant invention, nor do they suggest the polysiloxanes of this invention.
In a series of patents issued to Rody et al. in late 1980 and early 1981 (U.S. Pat. Nos. 4,232,131; 4,233,410; 4,233,412; 4,234,699; 4,260,689; 4,260,691; all divisions or continuation-in part of Ser. No. 896,676) there is a common disclosure of sterically hindered polyalkypiperidine compounds including polysilylesters and their use as stabilizers. None of these patents, however, suggest or disclose the polysiloxanes having sterically hindered heterocyclic moieties as defined by the general or specie formulas set forth in this instant specification.
In U.S. Pat. No. 4,684,726, issued to Greco et al. on Aug. 4, 1987, there is disclosed the reaction of silanes with compounds containing a sterically hindered amine group. However, there is no suggestion or disclosure on the use of polysiloxanes as reactants to produce the polysiloxanes of this invention containing the sterically hindered heterocyclic moiety.
United Kingdom Patent Specification No. 1,399,239, issued to Ciba-Geigy AG, published June 25, 1975, relates to novel piperidine derivative, however, none of the compounds are siloxane products.
The use of hindered amine light stabilizers (HALS) is discussed in the article "LLDPE and UV aging" by M. Cordonnier, Plast. & Rub. Proc. & Applic. 8 (1987) 23-27. Though reference to 3 HALS materials is made in Table 7 only one is specifically identified, Tinuvin 622, which is not a polysiloxane; there is no mention or suggestion of polysiloxanes.
In "Stabilization of filled polyolefins" E. Stengrevics et al., Plast. Compounding July/August 1987, 35, the use of oligomeric hindered piperidine derivatives as stabilizers is disclosed. However, none of these HALS compounds are polysiloxanes.
Processes for the production of "Polyiminooxy- and Polyaminoalkoxyorganosiloxanes" are shown by K. A. Andrianov et al., Dokl. Akad. Nauk SSSR, 20, No. 3, 616-619, Sept., 1972. This article shows the production of polysiloxanes, however, the compounds shown are not those of this instant invention.
In "The Antioxidizing Effect of Sterically Hindered Amines in Thermal Oxidation of Low Density Polyethylene", v. Dobrescu et al., Eur. Polym. J., 24, No. 3, 289-294 (1988) the stabilizing effect of the sterically hindered amine light stabilizers (HALS) shown in Table 1 on polyolefins was studied. None of the HALS compounds are polysiloxanes, nor are any siloxane compounds per se disclosed or suggested.